1. Field of the Invention
The present invention relates to a sample tube holder into which a plurality of sample tubes can be inserted, and a corresponding method for using the same.
2. Description of the Related Art
Many different types of racks or holders exist which are suitable for storing and transporting a plurality of containers, such as test tubes or the like, which hold a biological sample. However, many of these racks or holders are not configured to allow the test tubes or containers (hereinafter "test tubes" or "tubes") to be inserted directly into other devices which have a plurality of openings for accommodating the plurality of test tubes.
An example of such a device is a heating block having a plurality of cylindrical openings, each of which is configured to receive a single test tube. The heating block is thus able to heat the entire circumference of each test tube that is inserted into one of the openings and thus, effectively radiates and conducts heat to the samples present in the test tubes. This type of heating block is particularly useful as a lysing heating block that is employed in a DNA amplification process in which the cells in the samples stored in the tubes are heated to a temperature which causes them to rupture and release their DNA into the surrounding fluid in the test tube.
Most conventional test tube holders or racks (hereinafter "test tube holders") are incapable of inserting the test tubes into the corresponding holes of the heating block while the test tubes remain in the test tube holder, because these types of test tube holders typically have a base portion on which the bottoms of the test tubes rest when the test tubes are inserted in the holes into the test tube holder. These types of test tube holders are designed in this manner so that the base portion prevents the test tubes from sliding downward out of the openings in the test tube holder when the test tube holder is lifted. In other words, the openings in the test tube holder which accommodate the test tubes are usually large enough to allow the test tubes to freely slide in and out, and do not provide any force against the test tubes to prevent them from sliding out of the openings if the base of the test tube holder was not present.
Other types of test tube holders exist, such as that described in U.S. Pat. No. 2,979,210 to Patterson, in which slideable plates having corresponding openings are used to adjust the overall size of the openings in the rack to accommodate test tubes having different diameters. However, although the sliding plates can set the openings to essentially conform to the diameters of the tubes so that the tubes will stand upright in their respective openings with little or no play, this tube holder still requires a base portion for supporting the bottoms of the tubes because the tubes are capable of sliding out of the openings.
Another test tube holder is described in U.S. Pat. No. 5,133,939 to Mahe. The Mahe test tube holder includes a flexible member, having a plurality of holes, that is sandwiched between two plates having a plurality of holes which correspond with the holes in the flexible member. The diameters of the holes in the flexible member are slightly smaller than the diameters of the holes in the plates. Thus, when test tubes having diameters that essentially correspond to the diameters of the holes in the plates are inserted into the holes, the flexible member provides a frictional force about the test tubes and thus essentially restricts the test tubes from moving longitudinally in the openings. Because the test tubes are retained in the openings by the force applied to them by the flexible member, this type of test tube rack can be used with a dry bath incubator, for example, having a plurality of tube accommodating openings, to insert the test tubes directly into the openings of the dry bath incubator without removing the test tubes from the rack.
Nevertheless, this type of rack requiring a flexible member is somewhat ineffective because after many uses, the flexible member can become worn due to the frictional force exerted by the test tubes when being inserted into and removed from the openings. Furthermore, the properties of the flexible member can be adversely affected by the heat being applied to the test tubes and the rack by the incubator.
In addition, the flexible member allows the test tubes to shift and become slanted in their respective openings, thus making it difficult to align the tubes with the holes in the incubator. Also, the force applied to the test tubes by the flexible member is generally insufficient to secure the test tubes firmly enough in the openings so that an operator can unscrew the caps from the test tubes without grasping the body of the test tube to prevent the test tube from spinning. Furthermore, these types of multi-layered test tube holders can be complicated and expensive to manufacture.
Accordingly, a continuing need exists for an improved test tube holder that is capable of securely maintaining the test tubes in the openings of the holder without the use of a flexible material or a base which supports the bottoms of the test tubes.